1. Field of the Invention
The present invention relates to an interfacial connecting structure for triplate line in the band of millimeter wave.
2. Description of the Related Art
A conventional triplate line interfacial connecting structure is constructed as shown in FIG. 1 and FIG. 2, as follows. Namely, a first power feeding substrate 6 on which a first power feeding line 5 is formed and which is sandwiched by a first dielectric 4a and a second dielectric 4b, is disposed substantially in the middle of a first grounding conductor 1 and a second grounding conductor 2 to form a first triplate line. Further, a second power feeding substrate 9 on which a second power feeding line 8 is formed and which is sandwiched by a third dielectric 7a and a fourth dielectric 7b, is disposed substantially in the middle of the second grounding conductor 2 and a third grounding conductor 3 to form a second triplate line. Then, the first triplate line and the second triplate line are electromagnetically coupled with each other through a second slot 14 formed in the second grounding conductor 2.
A low dielectric constant material having a relative dielectric constant xcex51≈1 is used for the first dielectric 4a, second dielectric 4b, third dielectric 7a and fourth dielectric 7b in order to suppress a loss in the power feeding lines.
Further, a distance between the first grounding conductor 1 and the second grounding conductor 2 and a distance between the second grounding conductor 2 and the third grounding conductor 3 are set to less than substantially ⅕ of a line effective wave length (line effective wave length=free space wave length/square root of relative dielectric constant of a dielectric) of a frequency for use in order to avoid an occurrence of high order mode in a line under the frequency for use.
To couple the first power feeding line 5 with the second power feeding line 8 electromagnetically through the second slot 14 in a preferable condition, the second slot 14 has to be resonant at the frequency for use. Thus, as shown in FIG. 2, a resonator length L8 of the second slot 14 is set substantially xc2xd of the line effective wave length of the frequency for use and then, the second slot 14 has to be disposed at a position corresponding to line length L7 which is substantially xc2xc of the line effective wave length of the frequency for use from the connecting terminal end of each of the first power feeding line 5 and the second power feeding line 8.
Generally, a width of the second slot 14 is substantially 1/10 of the line effective wave length of the frequency for use.
By setting the resonator length L8 of the second slot 14 substantially xc2xd of the line effective wave length of the frequency for use, the second slot resonates at the frequency for use. Further, by setting the setting position L7 of the second slot 14 from the connecting terminal portion of each of the first power feeding line 5 and the second power feeding line 8 substantially xc2xc of the line effective wave length of the frequency for use, matching of the impedance estimated from the power feeding line to the second slot 14 is secured so that electricity is transmitted without reflection.
However, in the conventional triplate line interfacial connecting structure shown in FIG. 1, variations of the frequency relative to an error in the length of the resonator length L8 of the first power feeding line 5 is large and variations of impedance estimated from the power feeding line to the second slot 14 relative to an error in the setting position L7 of the second slot 14 from the connecting terminal portion of each of the first power feeding line 5 and the second power feeding line 8 is large. Thus, there is such a problem that the frequency characteristic becomes a narrow band.
Together with electromagnetic coupling between the first power feeding line 5, second power feeding line 8 and second slot 14, parallel plate components transmitted in lateral direction between the first grounding conductor 1 and the second grounding conductor 8 and between the third grounding conductor 2 and the second grounding conductor 2 are generated so that loss increases.
Further, if it is intended to achieve the conventional structure in a very high frequency band, for example 76.5 GHz, the resonator length L8 of the second slot 14 shown in FIG. 2 is substantially 2 mm and the width is less 0.4 mm, which are very fine dimensions for processing. Therefore, the second slot 14 is difficult to form by mechanical press processing or the like. Further, the setting position L7 of the second slot 14 from the connecting terminal portion of each of the first power feeding line 5 and the second power feeding line 8 has to be set as highly accurately as up to about 1 mm. Therefore, there is such a problem that a highly accurate processing method and an assembly method have to be always selected thereby leading to increased production cost.
An object of the present invention intends is to provide a triplate line interfacial connector excellent in preventing a loss and easy to assemble.
To achieve the above object, according to an aspect of the present invention, there is provided a triplate line interfacial connector for electrically connecting a first triplate line formed by disposing a first power feeding substrate, which is sandwiched by a first dielectric and a second dielectric and on which a first power feeding line is formed, substantially in the middle of a first grounding conductor and a second grounding connector and a second triplate line formed by disposing a second power feeding substrate, which is sandwiched by a third dielectric and a fourth dielectric and on which a second power feeding line is formed, substantially in the middle of the second grounding conductor and a third grounding conductor, wherein a first patch pattern and a second patch pattern are formed at a connecting terminal portion of a power feeding line of the first power feeding substrate and a connecting terminal portion of a second power feeding line of the second power feeding substrate, respectively, the first and second dielectrics are removed from around the first patch pattern while a first shield spacer and a second shield spacer each having a through portion relatively larger than the size of the first patch pattern and the first power feeding line connected thereto are provided at the portions in which the first and second dielectrics are removed, the third and fourth dielectrics are removed from around the second patch pattern while a third shield spacer and a fourth shield spacer each having a through portion relatively larger than the size of the second patch pattern and the second power feeding line connected thereto are provided at the portions in which the third and fourth dielectrics are removed, and a first slot is formed at a potion of the second grounding conductor, the portion corresponding to the first patch pattern and the second patch pattern.
According to a preferred embodiment of the present invention, a length of each of the first patch pattern and the second patch pattern in a direction in which each thereof is connected to line is substantially 0.38 times a free space wave length of a frequency for use, a dimension of the through portion of each of the first shield spacer, second shield spacer, third shield spacer, and fourth shield spacer in a direction that the periphery of the patch is connected to the line is substantially 0.6 times the free space wave length of the frequency for use, and a dimension of the first slot in the direction of the line connection is substantially 0.6 times the free space wave length of the frequency for use.
Further, according to a preferred embodiment of the present invention, the shape of each of the first patch pattern and the second patch pattern is circular, a diameter thereof is substantially 0.38 times the free space wave length of the frequency for use, the shape of the through portion around the patch in each of the first shield spacer, second shield spacer, third shield spacer and fourth shield spacer is circular, a diameter of the through portion around the patch is substantially 0.6 times the free space wave length of the frequency for use, and the shape of the first slot is circular while the diameter thereof is substantially 0.6 times the free space wave length of the frequency for use.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.